Imaging soft sphere packings in a novel triaxial shear setup

We describe here how to design a triaxial shear setup suitable for both stress and structure measurements on granular packings. Our novel setup makes use of refractive index matched scanning techniques. It can thus be used to study any kind of material compatible with that method. We describe in particular how to use hydrogel spheres, which we have found to have properties which make them particularly well suited for stress and structure measurements of granular packings. We discuss here some mechanical properties of hydrogel spheres and methods to use them in refractive index matched scanning devices such as the triaxial shear setup discussed.